1. Field of the Invention
The present invention relates to a heating apparatus adapted to be used with an image forming system such as an optical printer, copying machine or the like, and more particularly, it relates to a heating apparatus effectively used as a heating and fixing unit for the image forming system, and a heater used in the heating apparatus.
2. Related Background Art
Conventionally, heat roller fixing systems using a heat roller having a heater such as a halogen lamp therein have widely been used as a fixing unit for fixing a toner image onto a recording medium.
FIG. 9 shows a sectional view of a conventional heat roller fixing unit.
In FIG. 9, a heat roller 1 has a halogen lamp 28 therein. The reference numeral 2 denotes a pressure roller; 3 and 6 denote bearings; 4 denotes a drive gear for the heat roller; 5 denotes a ring for preventing the bearing 3 and the gear 4 from sliding off from the roller 1 in the thrust direction; 7 denotes a spring for biasing pressure roller 2 against the heat roller 1; 12 denotes a lead wire for supplying an electric power to the halogen heater; 13 denotes a conductive plate acting as an contact between the lead wire 12 and a power source; 14 denotes leaf springs for positioning the halogen lamp; 15 denotes an electrode of the power source side; 20 denotes an earth spring for earthing the heat roller 1; and 25 denotes insulating and low heat-conductive base portions made of ceramic and arranged on both sides of the halogen lamp.
Incidentally, the reference numerals 13a and 14a denote biases or screws.
In this way, the halogen lamp 28 is positioned and fixed by supporting the ceramic bases 25 of both sides of the lamp by means of the leaf springs 14 fixedly mounted on a fixed portion by the screws 14a.
However, in the above conventional example, since the halogen lamp 28 with the lead wires 12 must be inserted into the interior of the fixing roller 1 from one side thereof and the lead wire 12 must be drawn out of the interior of the roller from the other side thereof, the operability of the assembling is decreased and, in order to replace the halogen lamp 28, many parts including the leaf springs 14 must be disassembled.
Further, since the earth ring 20 electrically connected to the fixing roller 1 is mounted on the end of the fixing roller, the operability is further decreased. In addition, since the inner diameter of the fixing roller 1 cannot be reduced to keep the easy insertion of the lead wires 12 into the fixing roller, the fixing roller and accordingly the whole apparatus cannot be made small-sized.